1. Field of the Invention
The present invention relates to an apparatus for producing mineral fibers, and more particularly refers to a control valve for controlling the discharge of a stream of molten material such as rock or slag from the primary melter or holding device of the apparatus.
2. Description of the Prior Art
It has been conventional in the prior art to produce glass and mineral wool fibers by conveying a stream of molten material such as glass, rock or slag onto a rotating surface. The molten material is thereby centrifuged into the path of a high velocity stream formed or super heated steam or air. The centrifuged material originally in the form of finely divided molten streams is blasted by the steam or air and formed into solidified material of fibrous form. U.S. Pat. No. 4,106,921 discloses such a centrifugal rotating apparatus utilizing low pressure air to cause fiberization of the mineral fibers. In the apparatus of the prior art some difficulty has been experienced in carefully controlling the stream of molten material which is directed to the centrifugal fiberization apparatus. Moreover, because the melting of materials such as rock or slag and maintaining them at a low viscosity requires a high temperature, it has been difficult to prevent the destruction of valves used to control the melt flow. Moreover, after extended periods of operation, iron which is an impurity of the slag or rock settles to the bottom of the furnace in the form of molten metal and must be periodically drained from the furnace. The molten iron itself is very destructive of existing valve structures so that the valves must be replaced often.